Manufacture of ether derivatives of carbohydrates like cellulose



Patented June 13, 1933 UNITED STATES PATENT OFFICE AIRLIE W. SGI-IORGER,OF MADISON, WISCONSIN, ASSIGNOR TO 0. F. BURGESS LABORA- TORIES, INCL,OF MADISON, WISCONSIN, A CORPORATION OF DELAWARE MANUFACTURE OF ETI-IERDERIVATIVES OF CARBOHYDRATES LIKE GELLULOSE Application filed Augustll,1930. Serial No. 475,249.

This invention relates to new carbohydrate derivatives, especiallycellulose derivatives, and methods for making them. It relates moreparticularly to the hydroxy-alphyl ethers of cellulose and especiallythose hydroxy-alphyl ethers in which substantially less than onehydroxyl hydrogen atom in each cellulose unit is replaced by an alphylradical, and especially such compounds of this composition which are oflimited solubility in caustic soda solutions and are practicallyinsoluble in caustic potash solutions. This invention relates also to animproved method for making such derivatives whereby an olefine oxidecontaining an ethylene oxide group react with moist alkali carbohydrateand especially moist alkali cellulose. Some of the products possessphysical properties and characteristics suitable for the production ofwater-resistant, highly transparent films and filaments, plasticmixtures, insulating goods, finishing materials, etc. Other forms aresuitable for sizes, adhesives, filler for adhesives, etc. My new processpermits of the production of valuable intermediate forms of products aswill be explained hereinafter.

The raw materials suitable for my product and process include thefollowing: carbohydrates such as cane sugar, starch, glucose, celluloseof all kinds, materials containing cellulose, hydrated or hydrolyzedcellulose, raw or purified viscose (cellulose partially or completelyxanthated) before or after its spontaneous decomposition, otherrecovered cellulose, and some derivatives of cellulose, such aspartially esterfied, alkylated, or etherified cellulose, and suitableconversion products of cellulose which are as little degraded ordepolymerized as possible.

My etherifying agent is essentially a com-' pound containing an ethyleneoxide structure. It may be ethylene oxide as such or any of the olefinehomologs, such as propylene oxide, butylene oxide, amylene oxide or thehigher homologs which may be reactive oxides. Mixtures of these oxidesmay be used. The chlorhydrins corresponding to y these oxides may alsobe used in my process to make the derivatives of my invention' Otherchlorhydrins forming hydroxy-alphyl ethers as enumerated in thefollowing specification alsomay be used.

It has been found that the higher the number of carbon atoms in thereactive etherifymg compound the more diflicult it is to effect thereaction, that is,'more heat and time are requlred, so that the productsand process are practically limited to the compounds corresponding tothe homologs at the lower end of the olefine series.

Briefly, the process consists in treating the carbohydrate substancewith caustic alkali solution and subjecting the resulting alkalicarbohydrate to direct contact with the etherifying agent, that is, theolefine oxide, or a chlorhydrin corresponding to such oxide. Theseoperations usually result in an impure form of the desired carbohydratecompound. In practice, optional subsequent operations may be performedto purify the product and produce it in forms which are technically moreuseful.

It has been known that carbohydrates such as starch and cellulosecombine directlywith ethylene oxide to form compounds which may beethers, but which apparently are con stituted somewhat differently thanwhen made by my method. The methods which have been used for theirpreparation are such that the products have little or no commercialvalue because of various difficulties encountered in the process andtheir excessive cost. Furthermore, the products themselves are of such anature that they apparently have little practical application. Forinstance, if one part of cotton linters is treated with 10 partsethylene oxide at 100 C. for 10 hours a reaction probably occurs sincethe cotton linters seem to gain slightly in weight, but the resultingproduct appears to be only a more reactive form of cellulose which isinsoluble in a dilute caustic soda solution. On the other hand, by myprocess, if suflicient of the oxide reacts with alkali cellulose at roomtemperatures a product is formed immediately, which is completelysoluble in 10% caustic soda solution; or in case the amount of ethyleneoxide is insuflicient so that a small amount of reaction product isinsoluble in the caustic soda solution, practically complete apparentsolubility usually can be obtained by freezing the reaction product witha dilute caustic soda solution. Apparently the caustic alkali serves asa catalyst in promoting the reaction between the cellulose and olefineoxide.

Although the ethers of this invention are described as being partiallysoluble in caustic alkali solutions they form at least in part so-calledcolloidal solutions therewith as they apparently do not form truesolutions. The ethers are dispersed by the caustic alkali, which is thepeptizing agent. Throughout the application and claims when a solutionof the ether in caustic alkali solutions is referred to, itindicates asolution which may be partially or wholly colloidal.

I have found that it is possible to produce a reaction betweencarbohydrates, for example, cellulose, and ethylene oxide and/or some ofits homologs at room temperatures almost instantaneously, if thecarbohydrate is first treated with caustic alkali, presumably to form analkali compound therewith. The ethylene oxide or homologous oxide,preferably in gaseous form, is then brought into contact with theresulting alkali compound, preferably at room temperatures. Anexothermic reaction results which is vigorous, especially if the alkalicompound is wet. By the term wet I have reference to a materialcontaining the amount of liquid which remains after squeezing, wringing,or centrifuging out the excess liquid resulting from soaking thematerial in water or a water solution of a chemical such as causticsoda. No excess of oxide is needed as the reaction is practicallyquantitative. If insufficient oxide is added so that some of thereaction product remains insoluble in an aqueous caustic soda solutionat room temperature it is necessary only to freeze the product in thecai'lstic solution to obtain practically complete apparent solubility.Products made by reacting alkali cellulose with such oxides inproportions comparable to those heretofore made by direct union of theoxide and cellulose have different properties indicating that specificmethods of manufacture may determine specific properties in the productto meet the various uses to which the product may be put.

Although hydroxy-alphyl ethers of cellulose similar to those which Ihave discovered have been known and described, those others havecontained at least one hydroxy-alphyl radical per cellulose unit. Thoseethers were not of limited solubility in aqueous caustic alkalisolutions. Such prior hydroxyethers of cellulose have been produced bythe action of chlorhydrins such as ethylene chlorhydrin, propylenechlorhydrin and glycerol chlorhydrins on alkali cellulose withsubsequent purification operations if a pure product was desired. I havefound that with my improved method, I can use these same chlorhydrins toproduce alphylhydroxy ethers of cellulose containing substantially lessthan one replaced hydroxyl hydrogen atom per cellulose unit and whichare soluble in a 10% caustic soda solution but which are practicallyinsoluble or slightly soluble in a corresponding caustic potash solutionand also are limited in their solubility in dilute caustic sodasolutions of other concentrations. IVith my method it is possi ble tomake these derivatives in pure form without using purificationoperations as h ad been previously found necessary. My improved methodof reacting the alkali cellulose with the olefine oxide, especiallyethylene and propylene oxides, to produce both the hydroxy-alphyl ethersof cellulose containing less than one replaced hydroxyl hydrogen atomand those containing more than one replaced hydroxyl hydrogen atom percellulose unit, has advantages over the chlorhydrin method.

hen making cellulose compounds embodying this invention, the originalcellulose material, as hereinbefore described, may be used in the dry,air dry, moist or wet condition. It is first mercerized by steeping itfor a suitable length of time, such as from one to ten minutes at roomtemperature or slightly above, in a caustic alkali solution such as acaustic soda solution, which may range from 14% to 60% in strength butpreferably contains substantially less than 50% caustic soda. Themercerizing action is almost instantaneous. An equivalent caustic potashsolution may be used. lVhen using cellulose which is not dry, thequantity of water present may advantageously be considered when makingup the caustic alkali solution. The caustic soda solution itself absorbssmall amounts of etherifying agent. It has been found that a 30% causticsoda solution absorbs less ethylene oxide and homologous oxides thanweaker caustic soda solutions, whereas caustic soda solutions strongerthan leave an excess of caustic soda in the product which may be wastedin the subsequent operation. For example, I may use approximately 15parts by weight of caustic soda solution to one part of cellulose. Themixture may be gently agitated to insure uniform mercerization. As thecaustic soda in the solution present increases above 50%, the subsequentetherifying action is slower. Not only does the increased quantity ofcaustic soda present appear to slow down the reaction, but also anexcessive amount of water has the same apparent effect. Therefore, Iprefer to limit the water present, yet to provide a caustic sodasolution which does not contain more than 50% of alkali, and inconsequence, employ an alkali cellulose for etherification which ismerely wet with a solution of the desired strength and preferably of 30%strength.

After mercerization is complete, the excess caustic soda solution iseliminated by pressure, centrifugal action, or any other suitable methoduntil the cellulose content of the mixture has increased to at least20%, and preferably to between 25% and 35%. I prefer to call theresulting material a wet alkali cellulose. The etherifying agent is thenbrought into intimate contact with the wet alkali cellulose and theproportion of the reacting constituents is carefuly regulated. Althoughany of the etherifying agents and eellulosie materials heretoforementioned may be used, for purposes of illustration I first willdescribe in detail a process employing ethylene oxide and cotton lintersor some other form of high grade alpha cellulose, and one in whichrefrigeration is not necessary. Those skilled in the art may readilyadapt the following procedure to other cellulosic materials. Degradationof the cellulose through excessive ageing of the alkali cellulose tendsto make the etherified product water soluble and therefore must beavoided where water insoluble products are desired. Throughout thespecification, when cellulose or alkali celulose is referred to, it isunderstood that the cellulose has not been degraded sufficiently, unlesssuch degradation is mentioned specifically, to increase the solubilityof the resulting ether beyond the limits set for such solubility incaustic alkali solution.

Under ordinary conditions ofroom temperature (20 C.) and atmosphericpressure, ethylene oxide (boiling at about 10.7% C.) is a vapor. It isusually stored and shipped under pressure in metal cylinders. It may beconducted as a vapor directly from such cylinders to a suitable gastight reaction chamber containing alkali cellulose, the rate of flowbeing regulated in consideration of the rate of absorption by the alkalicellulose. To regulate the quantity of ethylene oxide used the cylindermay be supported upon weighing apparatus suitable for indicating itsdecrease in Weight. The ethylene oxide vapor also may be conducteddirectly to the alkali cellulose from an oxide generating chamber or itmay be generated in the alkali cellulose reaction chamber if desirable.Evacuation of the reaction chamber prior to the introduction of theoxide is desirable since it hastens the reaction and results in a moreuniform etherification. Ethylene oxide is introduced into the reactionchamber at a rate somewhat in excess of the rate of absorption and aftera suflieient quantity has been introduced, the flow is stopped. Themixture is agitated during all this time and agitation is continueduntil absorption to the extent desired is practically complete.

The etherifying reaction is exothermic and cooling may be necessary toprevent charring of the cellulose. I prefer to maintain the temperatureof the reacting mixture below 45 C. The agitation of the mixture alsoprevents local over-heating. It is not necessary, however, to keep thetemperature below the 15 C. specified since it only is necessary toavoid charring, which does not take place until a considerably highertemperature (about 100 C.) is reached. Stirring also ensures that theethylene oxide will reach all of the alkali cellulose. The etherifyingoperation may be continued until the supplied quantity of ethylene oxideis absorbed. lVhere it is not desirable to refrigerate the resultingether to secure practically complete solubility in dilute caustic sodasolutions it is necessary to react about 11% to 20% or more of ethyleneoxide (based on the cellulose in the alkali cellulose) with the alkalicellulose. If the refrigeration is practiced the larger amount ofethylene oxide may be reduced. A high grade cellulose such as cottonlinters requires a larger amount of ethylene oxide to secure completesolubility than a highly purified cellulose made from wood pulp, thelatter apparently being less resistant chemically.

The product obtained by the process outlined hereinabove probably is animpure ether of cellulose and ethylene oxide having a glycol structure,one impurity being the caustic alkali which, although present to ensuresuccess of the process, probably does not enter into the reactiondirectly and, after the reaction is complete, remains as an impurity.Where about 1 1% to 15% of ethylene oxide based on the cellulose contentis supplied and absorbed it is probable that two units of cellu lose arecombined with each molecule of ethylene oxide; hence the probableappropriate chemical designation is ethyleneglycol(di)- cellulose ordicellulosehydroxyethyl ether. A unit of cellulose is here defined as CII O Theoretically the ethylene oxide content of thedicellulosehydroxyethyl ether as represented by the formula below is13.6% of the cellulose content. When less than 15% of ethylene oxide isused the reaction between the alkali cellulose made from cotton lintersor other form of high-grade alpha cellulose and the ethylene oxide atabout 0 (I. must be carefully controlled so that only a small amount ofresidue insoluble in a dilute caustic soda solution remains. Under themost carefully controlled conditions I have made a compound with 11% to12% added ethylone oxide which was practically totally soluble (to theeye) in a 10% caustic soda solu tion. Even under these conditions themicroscope shows that the compound may not be entirely dispersed and theother may not be suitable for the highest grade products where a highdegree of transparency is desirable. Under ordinary conditions ofreaction it is necessary tosupply about 18% to 20% of ethylene oxide forcomplete solubility (using a high-grade cellulose) in dilute causticsoda solution, provided the reaction product is not subjected to a,temperature below freezing in the presence of the caustic soda solution.It is possible that some of the cellulose units may absorb more or lessthan the calculated amount of oxide. Furthermore, the ethylene oxide mayform a limited amount of ethylene glycol or diethylene oxide. Thesefacts may account for a measured absorption in excess of theoreticalpi'edictions. lVhen more than the preferred amount is used there may bewaste and the quality of the product is injured for certain purposes aswill be explained hereinafter. The properties of the product vary withthe amount of ethylene oxide absorbed which may be as high as 200%.

It is believed that under the above reaction conditions the union of thecellulose and ethylene oxide is etlected by the substitution of theethylene oxide radical tor the hydrogen atom of hydroxyl groupspreferably primarv) ot' a cellulose unit or of two or more linkedcellulose units whereby one valence of the oxygen atom of the oxide isreplaced by an liydroxyl hydrogen atom of the cellulose molecule to forman hydroxyl group attached to the ethylene radical. It is believed thatthe reaction "for the dicellulose ether takes place as follows:

CuH10O5C5H7O4.Oll2OH (/Ilz'CHz= Ethylene oxide C ll O:,Cr,l1 O.CIIzOCHz.OH20H Dicellulosehydroxyethyl ether Cellulose The foregoingillustrates the reaction on a primary hydroxyl group. More genericallyexpressed, the reaction is undoubtedly xou where XDH represents thecarbohydrates or its derivative.

The reaction for other carbohydrates such as starch, sugars, glucose,etc. probably takes place in a similar manner. When more ethylene oxideis absorbed than that shown by the above equation it is probable thatthe oxide replaces hydrogens in additional hydroxyl groups of thecarbohydrates or it forms chain compounds with the hydroxyl ot the addedethylene radical. Thus in further reaction it is possible that twodifferent products are formed or a mixture of two different products areformed. In the refrigeration method to be hereinafter more fullydescribed, it is probable that one ethylene oxide molecule orliydroxy-alphyl radical combines with aggregates consisting of fourcellulose units. The aggregate suffers less degradation when. less oxideor alphyl radical is added.

It acidified and then washed free of the resulting salts and remainingacids after such operations as have been described, the products retainthe physical form and megasoopic structure of the material from which itis derived, that is, in this case, the fibrous structure of cottonlinters or other alpha cellulose. After washing, it may be dried andshipped in such fibrous form or it may be stored indefinitely withoutdeterioration. In this form it is light, fiufiy, and very easilyhandled. The dicellulose compound and those compounds containing agreater proportion of cellulose are insoluble in water, alcohol, and abrine comprising a saturated solution of sodium sulphate slightlyacidified with sulphuric acid. The others of my invention differ fromthe ethers made previously and described in the literature and patentswith respect to their solubility in caustic alkalies. My ethers made byabsorption of than 20% of ethylene oxide by the soda cellulose, based onthe weight of the cellulose, are only partially soluble (less than 95%)in solutions containing more than 20% of caustic soda and in practicallyall stren ths of caustic potash solutions. If less than 0% of the etheris insoluble it is regarded as substantially soluble. These etherslikewise are only partially soluble in caustic soda solutions containingless than from 2% to 6% of caustic soda, the ethers higher in ethyleneoxide content being more soluble in the weaker caustic soda solutions.The reverse is true when the caustic soda solutions are in the the rangebetween 15% and 20%. The greatest solubility seems to be in to 15%solutions of caustic soda with the maxiu'ium at about 10%. These sameethers containing up to about 20% of added ethylene oxide are butpartially soluble in caustic potash solutions of any strength. Of theseethers, those containing from 13% to 14% to about 20% of added oxide,though only partially soluble, show the largest solubility of any of myethers in caustic potash solutions of about 15% to concentration,although most of them are less than soluble. The ether solubility ordispersion in a caustic alkali solution apparently increases more orless directly with the concentration of the etherifying agent. However,the solubility or dispersion of the ether may vary over a wide range ina small range o'l caustic alkali concentration as is shown, in theaccompanying solubility curves. At about an 8% ether concentration theclear solution is highly viscous so that solutions of much above thatconcentration are of little interest.

The solubilities given above and as delined for the claims are based onmeasurements made at room temperatures and on both dry and moist ethersmade from alkali celluloses in which the cellulose has not beensubjected to the action of caustic alkalies for an excessive length oftime, that is, the cellulose has not suffered enough degradation to makethe resulting ethers appreciably more soluble. Alpha cellulose derivedfrom wood pulp is the basic cellulosic material. The solubilities aredetermined by exposing the dry or wet precipitated ether to the actionof the caustic alkali solution for 24 hours at room temperature, theweight of ether conveniently being 2% of the solution weight. Thesolution is then centrifuged in an ordinary laboratory centrifuge. Thesolids thrown out of solution are washed by further centrifuging, throwninto a coagulating bath (alcoholacetic acid mixture), filtered, dried,and weighed. That portion of the ether which is thrown out of solutionsince it is not sufficiently dispersed to form a clear (to the eye)colloidal suspension or solution is regarded as not soluble since suchundissolved ether cannot be tolerated commercially where clear solutionsare required. For special purposes a greater degree of dispersion may berequired. The ether apparently disperses to varying particle sizesaccording to its concentration in the caustic alkali solutions. Itdisperses to a finer state of division, therefore indicating a highersolubility, the lower its ratio to the solution. The greater thedispersion the smaller the amount of ether which is thrown out bycentrifuging and the higher the apparent solubility. I have accordinglyused a low ether concentration when determining the solubility thereofsince solutions of such low concentration are below those of anycommercial importance, and, furthermore, a limited solubility of theether in such concentrations indicates a much lower solubility in thoseconcentrations of commercial importance. The solutions of low etherconcentration are also less viscous and more amenable to the necessarymanipulations.

The ethers should be substantially soluble in dilute caustic sodasolutions if they are to be used directly and are to be of anycommercial importance where transparency and freedom from insolubles isrequlred. Practically all commercial solutions are viscous and 5% ofinsoluble ether in such a viscous solution prevents it from beingfiltered to remove any considerable amount of 1nsoluble matter orotherwise manipulated effectively. For instance, if the ether is notsufiiciently soluble in caustic alkali solutions, a film made therefromis not clear and transparent, or if the soluble portion is filtered offafter diluting the solution sufficiently to make it filterable, it doesnot form a usable film because of the low ether concentration. Such lowconcentration solutions also cannot be used for making imitation silkfibers. A film made for commercial purposes should have a thickness ofabout .001 inch when dry.

A solution containing at least 5 of the ether is usually required tomake a satisfactory film. The solution should be practically clear tothe eye though it may even then contain insufliciently dispersedcellulose compounds which may prevent the making of a high gradeproduct. The solubility of the ether in caustic alkali solutions may beincreased by freezing it in the presence of caustic alkalies providedthat the ether is subjected to the action of the solvent caustic alkalidirectly after freezing, that is, the ether is not precipitated out ofthe alkali after the freezing operation. The freezing operationdisperses the ether more effectively and clear solutions are obtainedmore easily.

Whenever dilute caustic alkali solutions are mentioned in thisspecification they relate specifically to solutions containing from 2%to 25% of caustic alkali and sometimes may refer to solutions containingfrom 5% to 15% caustic alkali, especially in connection with causticsoda solutions.

Not only is the product containing a lower amount of ethylene oxide lesssoluble in dilute caustic alkali solutions but it is also cheaper tomake because of the relatively high cost of the etherifying agent. Italso has superior properties for many purposes. As hereinbef'oredescribed, the product formed by the absorption of less than about 11%to 15% of ethylene oxide generally does not form a clear solution whendissolved in a dilute caustic soda solution due to the incompletesolubility of the reaction product. The residual insoluble reactionproduct in the dissolved other is objectionable for most purposes andmust be removed. I have discovered that it may be made more soluble orentirely soluble by a suitable freezing operation. It is practicallyimpossible to filter this insoluble product (usually gelatinous fibers)from the viscous solutions of the ether in caustic soda which arerequired in the arts, and therefore other methods must be used.

In the accompanying drawing:

Fig. 1 illustrates the apparent solubility of a series of ethers incaustic soda solutions;

Fig. 2 illustrates the increased solubilities over those in Fig. 1produced by the freezing process of this invention;

Fig. 3 illustrates the apparent solubilities of a series of ethers incaustic potash solutions;

Fig. 4; illustrates specifically the effect of freezing to increasesolubility.

I do not intend to bind myself closely to the properties of the ethersas indicated by the curves in the figures, since the properties arevariable and are determined by the various factors herein described. Thecurves are given only to illustrate properties graphically forvisualizing the numerous general statements herein made, and to permitone to recognize the direction in which the proper ties change withchanges in the process.

The data for curves which appear in full lines have been ratherquantitatively found to locate the same on the chart. The dotted linecurves are predicated on many qualitative observations, and considerableexperience within the ranges covered, and represent generally what Ibelieve to exist.

In Fig. 1, the curves are derived, as by a standardized test, bysubjecting two parts by weight of an ether containing various amounts ofethylene oxide to solution in 100 parts by weight of various strengthsof caustic soda. The percent of the exposed ether which is dissolved ordispersed in the caustic soda is plotted vertically against the strengthof the caustic soda solution. Curve 10 corresponds to thetetra-cellulose ether, containing about 6.8% ethylene oxide. Curve 11corresponds to a dicellulose ether containing about 13.6% ethyleneoxide. Curve 12 corresponds to a mono-cellulose ether containing 27.2%ethylene oxide. Curve 13 corresponds to a more complex ether containing40.4% ethylene oxide.

Fig. 2 is derived in the same way as the curves in Fig. 1, but theproduct was frozen, as elsewhere described, to increase the solubility.Curves 14, 15 and 16 correspond respectively to the materials of curves10, 11 and 12 of Fig. 1. The two figures show the increase in solubilitywhich is most notable in the more dilute caustic soda solutions.

Fig. 8 relates to caustic potash solutions and indicates the lessenedsolubility therein. Curve 17 represents a dicellulose ether withoutfreezing, and curve 18 indicates the increase over 17 by freezing theproduct. Likewise, curves 19 and 20 indicate respectively the relativesolubilities of a mono-cellulose ether, unfrozen and frozen.

In Fig. 4 two curves are shown based upon the following table of data:

Solubility of an ether containing 8% ethylene amide in caustic alkalisolutions Percent of exposed ether which is'insoluble at roomtemperature Parts ether KOH ig? 8% NaOH parts 8%* 15% solvent With WithWith freezing freezing freezing freezing freezing The ether waspractically entirely insoluble at room temperature in 8% KOH.

Curve 21 represents the amount of undissolved ether at the variousconcentrations when solution is effected without freezing. When the samesolution is frozen, as herein described, the insoluble portion issubstantially all rendered soluble over the range indicated. The curve22 represents the small amounts found undissolved after freezing. Theshaded area 23 therefore represents graphically the advantage of thefreezing process.

The low partial solubility of my ethers in caustic potash solutions isalso of further technical importance. If cellulose is mercerized withcaustic potash and then etheritied the resulting ether may be washeddirectly with water to remove the caustic potash contained therein sincethe ether is practically insoluble in most caustic potash solu tions.This is not possible with the ether made from soda cellulose. The use ofthe caustic potash therefore obviates the necessity of neutralizing thecaustic alkali in the ether with an acid which makes it impossible torecover the alkali. On the other hand the caustic pot-ash solutionwashed from the ether may be evaporated to mercerizing strength andagain used. Last traces of caustic potash in the ether may beneutralized by means of an acid.

I have found that if the alkali cellulose, mercerized as previouslydescribed and then subjected to ethylene oxide or homologous oxides attemperatures below charring and preferably at or about roomtemperatures, in an amount which does not give a product completelysoluble in caustic soda solution, is then refrigerated until the causticsoda solution freezes, the product becomes more sol uble 0r completelyapparently soluble. The insoluble fibers have been so modified by theetherification process that they require only the change, perhaps only amechanical disin;

tegration, produced by freezing to disperse and render them apparentlyand effectively soluble in the caustic soda solution. In this way I maymake a product practically completely soluble in dilute caustic sodasolutions (5% to 15%) although containing only about 7% to 8% ofethylene oxide based on the weight of cellulose used. As an example, anether containing 8% ethylene oxide, when subjected to the action of 12times its weight of 8% caustic soda showed 34.1% insoluble in 24 hoursat room temperature. A similar mixture when subjected to a temperatureof 20 C. for the same length of time showed but 1.20% insoluble. Thisindicates that one ethylene oxide unit combines with four units ofcellulose to form ethyleneglycol (tetra) cellulose ortetracollulosehydroxyethyl ether in which compound the oxide is in theproportion of 6.8% of the cellulose content. I/Vith less than thisamount of oxide a more or less cloudy solution is formed, even when theether is dispersed by freezing, showing that a portion of the celluloseether compound or reaction product is insoluble. I have, however, madereaction products containing as low as 3.5% added ethylene oxide which,with freezing, are largely soluble in a 10% caustic soda solution. Suchsolutions containing undissolved cellulosic materials in suspension maybe technically useful and are within the scope of my invention. Asanother example, an ether containing 12% to 14% of added ethylene oxidemay appear completely soluble to the eye but contains dis persedparticles sufficiently large to prevent making a product of the highestdegree of transparency. A freezing operation will further disperse theseparticles to produce a solution which yields films of the highesttransparency.

The compound formed which contains less than 13.6% of added oxidenecessary for the ethyleneglycol (di) cellulose ether and esecially thecompound containing less than 10% of added oxide or more than about 3units of cellulose has many desirable properties. The cellulose compoundof ethylene oxide of these proportions which, when thrown out ofsolution when the alkali solution reacts with an acid or otherprecipitating agent, is tougher and stronger than one which contains ahigher percentage of oxide. It gives a film which is flexible and may bestretched without the addition of glycerine. The superior physicalproperties of the product indicate that the cellulose has undergonelittle degradation. It furthermore makes possible the use of variouschemical wood pulps for the manufacture of high grade films andfilaments now only possible when made with specially prepared wood pulpor cotton linters.

Films and filaments and the like may be made from the hereinbeforedescribed ethers containing an ethylene oxide content up to 20%. If theadded ethylene oxide is in ex-, cess of approximately 20% of the weightof cellulose in the alkali cellulose the films and filaments becomesofter and slimier when wet. The greater the excess of oxide the morepronounced these characteristics become. Furthermore, with increasedalphyl content the product tends to become more soluble or entirelysoluble in caustic potash solutions, very dilute caustic alkalies andwater. This ordinarily is not desirable. I therefore prefer making acompound that consists of substantially less than about one molecularweight of ethylene oxide to one unit of cellulose, and containingusually less than 20% of added ethylene oxide. This applies also to thecompound whether made with ethylene oxide or ethylene chlorhydrin.

When making films and filaments and the like the ether is dissolved in acaustic soda solution, a weak caustic soda solution of about 2 to 3%strength being used for an ether of about 20% added ethylene oxidecontent and about 5% caustic soda for one which has had to be frozen inorder to make all of the ether soluble. Sufiicient caustic soda solutionmay be used to produce a solution containing any desired amount ofcellulose ether, the ether concentration usually being from 6% to 8% or9%.

The solution is usually clear, but as a precaution may be filtered toremove what ever dirt or other solids, or undissolved matter that may bepresent. Its viscosity may be made such that it is capable of beingextruded from dies into a number of forms, such as films or filaments,continuous tubing, or made into bottle caps, insulating goods, and thelike. It may be extruded into a coagulating bath similar to thatemployed in the manufacture of films, filaments, and the like fromviscose, namely, of the approximate composition: 10% sulphuric acid, 20%sodium sulphate and the usual organic compounds such as glucose, andinorganic salts such as zinc sulphate, magnesium sulphate, etc. Theproduct sets into a transparent, non-fibrous, solid substance which,after washing in water has a good wet and dry strength. Threads andsheets made from a new product possess good physical properties. Thefilms or filaments so made are clear and uniform in color, often do notrequire bleaching, are hard and firm in texture, and possess goodtensile strength.

Following is an example in which refrigeration is used. The cottonlinters or chemical wood pulp are mercerized in the usual manner ashereinbefore described. The excess caustic alkali is removed asdescribed. The alkali cellulose is exposed to the desired amount ofethylene oxidesay not more than 6.8% to 10%-until the oxide is absorbed.lVater is added to this product until the strength of the caustic sodasolution (the cellulose ether not included) is reduced to 2% to 10%,preferably 4% to 6%, the optimum being about 1.7 5 Caustic sodasolutions of 2% to 10% strength start freezing at from 0.3 C. to 10 C.If sodium chloride or other salts are present in the caustic sodasolution the percentage varies accordingly from those given. The mixtureis refrigerated to such a temperature that a mass of crystals of iceform and preferably until the caustic soda solution freezes. Althoughthe water starts freezing and ice separates from a solution containingless than 20% caustic soda the residual caustic soda solution itselfdoes not freeze until a concentration of 20% is reached. A 20% causticsoda solution freezes at 20 C. This temperature is the most effective.Lower temperatures may be used. Long exposure to these low temperaturesis not harmful to the product. The frozen mixture has a cheesyconsistency and contains ice crystals and hydrated caustic soda crystalsif the temperature is maintained at 20 C. or lower. The mass is allowedto melt and come to room temperature. If necessary more caustic sodaadded, and preferably to the melting mass to prevent geling at roomtemperature, since the ether containing 7% ethylene oxide requires atleast a 6% caustic soda solution to produce complete solubility. Thehigher ethers permit the use of weaker caustic soda solutions. Thecompound of cellulose and ethylene oxide or homologous oxides on meltingis transformed into a syrupy solution in the caustic soda. Thissolution, when made under the optimum conditions, is practically freefrom insoluble cellulosic materials and may be treated in much the samemanner and used for many of the same purposes as the product obtainedwhen 13% to 20% of the ethylene oxide is present in the compound.

Its superiority for certain purposes has been discussed previously.Although a specific procedure has been given the amount of ethyleneoxide and the refrigerating tem peratures may be varied over a widerange to secure specific products without departing from the scope of myinvention. Refrigeration sometimes may be used to advantage for productscontaining a high percentage of oxide if a small amount of insolublecellulosic material remains after dissolving the reaction product in acaustic soda solution.

In the above example in which refrigeration is used the cellulose ismercerized with a to 30% caustic soda solution, and then squeezed toremove excess caustic solution. After ethcrification when water is addedto decrease the caustic soda concentration to about 4.75% for thefreezing operation, the ether concentration in the final solution is toolow (about to 6%) for many purposes. The preferred procedure which maybe used to increase this ether concentration, and which decreases theamount of material which has to be frozen, to remove about of thereaction product after etherificat on before dilution with water, andneutralize the alkali with acid. The ether is then washed and is addedto the balance of the reaction product. The entire mass is then dilutedwith water to reduce the caustic soda solut on strength to 4.75%. It isthen frozen, after which it is thawed with proper caustic soda addition.This produces an ether concentration of 8% to 8.50% which is desirablefor many purposes. If desired the entire reaction product may be firstacidified, washed, and then frozen in caustic soda solution.

Although caustic soda is the specific caustic alkali specified duringthe refrigerating operation it is possible to use caustic potashsolutions though the concentration limits are narrower. It is possibleby the refrigeration method to increase somewhat the very limitedsolublity in dilute caustic potash solutions (10% to of the etherscontaining a low percentage of hydroxy-ethyl radical. These ethers whichshow an increase in their very limited solubility in dilute causticpotash solutions after freezing, do not retain this increase insolubility after being again precipitated from caustic alkali solution,unless subjected to refrigeration again. These results are similar tothose obtained when caustic soda solutions are used.

It is also possible to remove small amounts of insoluble reactionproduct from hydroxyethers containing a low percentage of hydroxy-alphylradical by dissolving the etherilied reaction product in a dilutecaustic soda solution (about 6% to 10%) and filtering off the smallamount of insoluble matter. The ether concentration, however, must below to filter the solution. As this procedure results in a solution ofether too dilute for most purposes it is necessary to evaporate off theexcess water or to precipitate the ether from it. After precipitationand wash ing it is redissolved to the desired concentration in causticsoda solution. Refrigeration may be used to aid solution. This methodhas too many disadvantages for practical purposes and also tends todegrade the cellulose, thereby increasing the solubility of the finalether in caustic alkalies.

It is possible also to react the ethylene oxide with cellulose directlywith or without a catalyst as has been previously known in the art, andthen refrigerate these products with caustic soda solutions, therebyrendering soluble, or increasing the solubility of, those compounds ofethylene oxide and cellulose which have been regarded as insoluble incaustic soda. 1 have treated wood pulp with 12% of ethylene oxide, usinga ten'iperature of 100 C. and pressure, in the absence of alkali,producing a product in soluble in dilute caustic soda solutions at roomtemperatures. The entire reaction product was then frozen in a dilutecaustic soda solution and on. melting the solubility of the product indilute caustic soda solution seems to have increased, judging by theincrease in the amount of gel-like material.

I am able by my improved process to make those compounds which arelowest in cost and most useful in the arts and which apparently were notproduced by the processes heretofore known. Those compounds which werenot previously produced and which are most valuable are those which areinsoluble in wa ter and practically or almost insoluble in dilutecaustic potash solutions, and which have a limited partial solubility indilute caustic soda solutions as hereinbefore described, and whichcontain substantially less than one molecular weight of olefine oxide incombination with one unit of cellulose (6 11 0 and especially thosecontaining less than one molecular weight of oxide to two units ofcellulose.

Although hydroxy-alphyl ethers of cellulose have been made by reactingupon wet alkali cellulose with a halohydrin of a. polyalcohol the ethersresulting from that reaction have been described as being easily solublein aqueous caustic alkalies and as being derivatives in which at leastone hydroxyl hydrogen atom of the cellulose is replaced by anhydroxy-alphyl group. The relatively large amount of ether-formingcompound thus introduced into the cellulose molecule by the above methodapparently resulted in the production of derivatives which showed a highsolubility in the caustic alkalies. Such compounds are of littlecommercial importance. I have found that it is not necessary to use thehalohydrin since I apparently can produce the same compounds byutilizing the gaseous oxides which result when the halohydrin reactswith caustic alkali. I also have found that it is possible to apply therefrigeration principle to the cellulose derivatives formed by treatingthe alkali cellulose with the halohydrin.

Olefine chlorhydrins, such as propylene and ethylene chlorhydrins, andglycerol monochlorhydrin, also known as alpha monochlorhydrin, maybeused to produce the by droxy-alphyl others. The glycerol oxidecorresponding to the glycerol monochlorhydrin is very difficult to makeand therefore is not at present of importance for the commercialproduction of the dihydroxy-propyl ether of cellulose. If hydroxy-ethersare to be produced which have substantially less than one hydroxy-alphylradical per cellulose unit I have found that it is better to use thesechlorhydrins in practically dehydrated condition. It is also better touse a stronger caustic alkali solution for mercerizing the cellulose.Instead of using the 30% solution which I prefer with the ethylene oxidemethod I prefer using about a 40% caustic soda solution. If thecommercial ethylene chlorhydrin, which contains about 60% water, isused, the results are unsatisfactory and the reaction is incomplete. Alarge amount of cellulose apparently remains unacted or only slightlyacted upon by the chlorhydrin. The derivatives made by using thechlorhydrins and containing a large proportion of cellulose to theethylene oxide or hydroxy-alphyl content, that is, from two to fourcellulose units to one of the oxide, contain a certain amount ofcellulose reaction products which are insoluble in a dilute caustic sodasolution and it becomes necessary to freeze the solution as previouslydescribed to make these insoluble products more soluble. The sodacellulose after being treated with the chlorhydrin contains not only thehydroxy-ether and the insoluble particles of cellulose compound but alsothe sodium chloride which is formed by the chlorine in the chlorhydrin.This mixture may be frozen directly without the removal of the sodiumchloride or the mixture may be neutralized, washed to remove the sodiumchloride, and then frozen. These procedures will be further illustratedin specific examples.

Using cotton linters as a base the viscosity of the product whendissolved in dilute caustic alkalies often becomes excessive forordinary purposes. I find that this viscosity can be reduced and thetendency to solubility in water increased to any desired extent withoutchanging the concentration of the solution, by ageing thealkali-cellulose before etherification or by ageing the unwashed andundried etherified alkali-cellulose before solution, or even by simplyageing the resulting alkaline solution of the ether. Higher temperaturesin ageing produce a lower viscosity, and increase the solubility.Excessive lowering of viscosity may result in derivatives that produceweak films or filaments. Higher temperatures in the etherification donot appreciably increase solubility. There seems to be no directrelation between viscosity and solubility, but depolymerization of thecellulose both lowers viscosity and increases solubility. Higherproportions of oxide lower viscosity and increase solubility.

As mentioned heretofore, I may use cellulosic material other than cottonlinters. Cotton linters are probably the least depolymerized form ofcellulose obtainable. If a more depolymerized form such as chemical woodpulp is used, the ether obtained is made water soluble more easily, thesolubility increasing with the extent of depolymerization of the rawcellulosic material. However, even depolymerized celluloses such asartificial silks, consisting of cellulose regenerated from viscosesolutions, form water insoluble products if treated with moderateamounts of ethylene oxide in the presence of caustic alkali. Suchcellulose (without mercerizing) forms water soluble products withethylene oxide directly if heated with an excess of oxide at 100 C. fora number of .hours, Whereas the same treatment with cotton linters orwood pulps results in a product which cannot be distinguished from theoriginal cellulose except that it is only slightly more reactive (e. g.to esterification) but it is not soluble in water, caustic soda, ororganic reagents at ordinary temperatures. The etherifying action whichoccurs when the oxide reacts with the alkali cellulose therefore must bedifferent than when the oxide reacts directly on the cellulose. Thereare many practical industrial applications for a water soluble productin a dry fibrous form or in aqueous solution. Some of the uses to whichit is applicable are: size for textiles,

adhesives, filler for adhesives, base for explosives, etc.

The formation of a water soluble product from alkali cellulose dependson the kind of cellulose (wood cellulose, hydrocellulose, etc.) and theageing of the alkali cellulose, or ether solution, etc. as previouslyexplained. The process for producing the soluble product from ordinarypulp is simple. The raw cellulosic material such as chemical wood pulpis mercerized to obtain alkali cellulose, allowed to stand for 2d hoursin limited contact with air, and ctherified with a large amount (75% to90% or more) of ethylene oxide as above described. The oxygen of the airoxidizes the cellulose and renders it more easily dispersible. Inpermitting contact with air the material is best maintained in a loosefluffy condition in a container having a loosely fitting cover throughwhich air may enter. Further standing in contact with excess alkali maybe necessary. To form the dry, fibrous product, the impure ether isneutralized with a suitable acid, washed with alcohol, and dried. Toform the aqueous solution the impure ether is dissolved in water orcaustic alkali solution. It then may be neutralized with suitable acidsuch as acetic acid, and the resulting salts may be washed out with anorganic solvent such as alcohol, or may be removed by dialysis or bydrying the neutral product and leaching the salts therefrom with anon-aqueous solvent. After the salts are removed, the material may bedissolved in water and the viscosity of the solution may be regulated toany desired value. Such material is valuable as an adhesive, eitheralone or with sodium silicate, and may also be used as a filler for inksor other similar materials as enumerated above.

The advantages of my process over the viscose process for themanufacture of films, filaments, etc., lie in obtaining more stablecellu lose solutions and products which require neither desulphurizingnor bleaching. An additional advantage is realized by re-dissolvingwaste and se aps in a caustic alkali solution and using it for anydesired purpose for which a fresh solution may be used. Furthermore noodors nor poisonous gas are liberated by the coagulating bath. Viscosemust always be fashioned into its final form after a period of carefu lycontrolled ageing whereas my ether, once purified and freed from causticsoda, may be stored indefinitely in the dry state, or in water if a moldpreventive, such as forn'laldehyde, is present. It may be used at anytime. In the presence of dilute caustic soda solution, the solutionshows rel atively little change with age as compared to similar viscosesolutions. Of course, either product may be stored safely ifrefrigerated. Furthermore, the sodium cellulose xanthate, of whichviscose is comprised, is unstable and is subject to spontaneousdecomposition, whereas my product is relatively stable and suffers onlya slight drop in viscosity while ageing in dilute caustic sodasolutions. A further advantage of my product lies in the ease andsimplicity with which the washing of the coagulated product isaccomplished. Washing in water is all that is required, whereas in thecase of viscose, the large quantities of sulphur in the impurecoagulated product must be eliminated and a number of washing andbleaching operations must be performed.

The ethylene oxide or other olefine hydrocarbon oxide may be dissolvedin benzol or some other non-reactive organic solvent and this solutionused to react with the alkali carbohydrate. A specific illustration isgiven hereinafter as Example V.

Although I prefer to use the etherifying agent in the vapor phase, I mayuse it in its liquid phase as well as in a solution. Example VI givenhereinafter illustrates the use of an oxide in its liquid form.

The compounds of cellulose and propylene oxide, butylene oxide, andamylene oxide, may be prepared in a manner similar to the method usedfor the preparation of the ethylene oxide compound with due regard tothe slight differences in the physical and chemical properties of theseoxides. The slight differences in manipulation necessary will beunderstood by those ski led in the art. The resulting compounds havethose differences in their properties as are to be expected in a seriesof such compounds. If propylene oxide is used as the etherifying agent,the following example shows how it may be used without freezing. Thecarbohydrate such as celllt lose is treated with alkali by steeping andthen removing the excess as hereinbefore described for etherification byethylene oxide. The resulting alkali cellulose is then treated with ameasured amount of propylene oxide (boiling point C.) in a closedcontainer at about 85 C. to 40 C. In a specific instance when 126% ofpropylene oxide was absorbed, the reaction product as a 6% solution ofether in dilute caustic soda, resulted in a translucent syrup containingmany undissolved fibers; at 17.6% there was increased solubility butmany undissolved fibers; at 22.4% most of the fibers were soluble in acaustic soda solution which could be filtered to a clear solution; andat 28.3% there was perfect solubility. The end product is anhydroxy-propyl ether of cellulose. The 12.6% propylene oxide compoundmay be frozen to form upon melting a practically perfect solution indilute caustic soda. The properties of the caustic soda solution of thiscompound are very similar to those of the corresponding ethylenecompound, and the films coagulated therefrom are comparable to thosemade from the ethylene compound. The ethylene and propylene compoundsmay be mixed or formed by the mixed oxides and sometimes used toadvantage to replace the separate compounds.

When using chemical wood pulp instead of cotton linters to produceethyleneglycol(di) cellulose ether or the other compounds containing ahigher proportion of the etherifying reagent, I prefer to steep thesheets of pulp in about 15 parts of 18% to 25% canstic soda solution,and then squeeze to form an alkalicellulose containing from 25% to 35%cellulose. This alkali cellulose is then etherified in a closedcontainer with ethy ene oxide at room temperature. Ifethyleneglycol(di)cellulose ether is desired about 1 1% of the oxidebased on the cellulose content is used. The balance of the procedure isthe same as before. Films and filaments made from the wood pulp compoundare weaker when wet than a similar compound made from cotton linters.

If compounds of the carbohydrates not of a. cellulosic nature are to beformed, the procedure which is followed is similar to that used withcellulose, giving due regard to the differences in the chemical andphysical properties of these compounds. Such carbohydrates may bestarches, sugars, such as cane sugar, glucose, etc., and include suchcarbohydrate derivatives as contain hydroxyl groups that are reactivewith ethylene oxide. These materials after treating with alkali reactwith ethylene oxide and propylene oxide and other oxides of the olefineseries with great vigor. The large amount of heat liberated readilyproduces a sutficient rise in temperature to cause charring if thereacting materials are not cooled. A large excess of ethylene oxiderenders the product soluble in alcohol. Glucose and cane sugar and othersimilar carbohydrates may be etherified in a like manner to starch.Refrigeration may be used with the starch as with cellulose but theredoes not appear to be any advantage gained because all of the productsare water soluble, including the alkali starch.

Throughout the specification ctherification has been used to denote thereaction in the presence of alkali between the carbohydrate and thereacting oxide, or chlorhydrin. The product resulting from the additionof suitable alkali to the various carbohydrates is called alkalicarbohydrate and in the case of cellulose alkali cellulose. The finalproduct also has been called an ether although the definite structure ofthe product is not known.

It is probable that the cellulose ethers made according to my inventionare hydroxy-alphyl ethers of cellulose. Those ethers made by reactingthe alkali cellulose with ethylene oxide or ethylene chlorhydrin areprobably hydroxy-ethyl ethers of cellulose, those made by reacting thealkali cellulose with propylene oxide or propylene chlorhydrin arehydroxy-propyl ethers of cellulose, those made by reacting alkalicellulose with glycerols monochlorhydrin are dihydroxypropyl celluloseethers.

Throughout the specification I use the term alphyl as indicating aradical of the aliphatic series inasmuch as the term alkyl which issometimes used to make this distinct reference is frequently indicativeof both aliphatic and aromatic radicals. The term alphyl is specific tothe aliphatic series in the same manner as aryl is specific to thearomatic series. See Richters Organic Chemistry, Vol. 1, page 43, firstEnglish Edition. 1916. The term caustic alkalies so far as I havereduced the invention to practice refers only to the hydrates of sodiumand pe tassium, but in the claims would not exclude the use ofhydroxides of other monovalent alkali metals.

Although my process may be applied to carbohydrates in general itsgreatest im portance at present seems to be in its application to thosecarbohydrates that are polysaccharides, especially cellulose. Bycarbohydrate I refer especially tothe natural sugars, starches, andcelluloses, and substances related to them. These polysaccharides maycontain tWo or more units of 0 11 0 The cellulose molecule which has notbeen depolymerized, may contain four such units and my experimentsindicate that four or possibly more of such units will combine with oneor more ethylene oxide molecules to form a compound soluble in dilutecaustic soda solution (5% to 15%). The carbohydrates like glucose,which, on the other hand, consist of one such unit, probably united inequimolecular proportions with the oxide.

It is to be observed that in the process of carrying out the reactionsof this invention it may be difficult to control the reaction so thatevery unit of carbohydrate is similarly combined with an oxide molecule.Some units of carbohydrate may be deficient in and others may beover-supplied with the oxide, while the average aggregate and thegreater percentage of all the aggregates may be similarly combined.Therefore in. the appended claims it is contemplated that the productsclaimed are not composed entirely, but only predominantly, as specified.Whenever the percentage of olefine oxide or alphyl radical is specified,it refers to the added amount rather than the actual amount. This isnecessary because of the difiiculties encountered in analyzing thereaction products to determine their exact constitution.

l-Vhenever a reference is made to olefine oxides containing an ethyleneoxide group it is intended to cover those oxides in which the oxygene islinked to two adjacent carbon hydrogen groups thereby forming anethylene oxide group within the olefine. WVhenever a non-substitutedolefine oxide is referred to this does not cover the homologous oxidesof the series. Propylene oxide may, for example, be called methylethylene oxide and may possibly be regarded as a substitute oxide but byme it is not so regarded.

The following specific examples of the invention are given by way ofsummarizing the invention in its various modifications. Qthermodifications are contemplated by the appended claims.

Example l.ellnlose-ethylene oxicle water insoluble compound suitable forfilms, filaments, eta, containing 20% ethylene oxicle baserl on originalcellulose 100 parts by weight (dry weight) of cotton linters arethoroughly stirred into 1500 parts by weight of 30% caustic sodasolution. After stirring for several minutes to insure thorough wettingof the linters by the caustic soda solution, the linters, now changed1nto alkali cellulose, are passed through squeeze rolls to remove theexcess caustic soda solution and to increase the cellulose content ofthe mixture to about 30%. The mixture after shredding is a wet, fluffy,fibrous mass. It usually is not allowed to age more than 24 hours atabout 20 C. It is put into a tightly closed reaction chamber in whichstirrers keep the alkali cellulose thoroughly agitated. (Fooling meanson the exterior of the reaction chamber may be necessary if theetherifying action is too violent. It is preferable to evacuate thereaction chamber prior to the introduction of the oxide this hastens thereaction and allows the reaction to proceed more uniformly throughoutthe alkali cellulosc. )Vhile the alkali cellulose is being stirredvigorously about twenty pounds of gaseous ethylene oxide are admitted ata rate which does not allow the reacting mass to go over a temperatureof 100 C. For the best results the temperature is kept below 45 C. Theresulting product is still fluffy and retains the physical megascopicform and structure of the linters. This product then may be processed intwo ways:

(A) To neutralize the excess caustic soda, it may be treated with adilute acid, preferably hydrochloric or sulphuric of about 5% tostrength. If the fibrous compound is stirred into the acid vigorously,local formation of gel spots may be prevented and the resulting productretain the fluffy fibrous forms of the fibrous linters. After thecaustic soda is neutralized the product consists of thecellulose-ethylene oxide compound, hydroxy-ethyl cellulose other. It maybe washed with water to neutrality and then dried. The resulting productstill retains its fibrous, fluffy condition and may be keptindefinitely. It may be dissolved in dilute caustic soda solution at anytime and utilized as described in the following paragraph (B).

(B) The fluffy alkaline cellulose-ethylene oxide product is stirred intowater so that the cellulose concentration is from about 5 5% to 8%(based on the original weight of air dry cellulose used). There shouldbe enough caustic soda presentin the product so that the dilutedsolution contains at least 2% and preferably 2 of caustic soda. If theconcentration is below this enough caustic soda is added to bring it upto the desired amount. The cellulose compound forms a clear viscoussolution in the dilute caustic soda. This solution may be filtered toremove any undissolved impurities. If the solution is too viscous forthe next operations it may be aged to reduce this viscosity Withoutdecreasing the cellulose concentration. This solution is then passedthrough suitable dies or formed on suitable shapes to make films,filaments and other products. It then is passed directly into an acidcoagulating bath such as 5% sulphuric acid which may contain of sodiumsulphate. The caustic soda is neutralized forming a film, filament orother article of water insoluble cellulose-ethylene oxide or cellulosehydroxyethyl ether gel. The gel is washed with water and dried. Otheroperations may be carried out on the formed gel before drying dependingupon the use to which it is to be put. Fillers and pigments may beincorporated in the viscous alkaline solution if desirable.

Example [[.Ma, eing compounds containing 7% o ethylene oxicle usingxefrlgexation (A) Sheets of chemical wood pulp high in alpha celluloseare used as the raw material in this case. Sufficient Wood pulp is takenso that it contains 100 parts by weight of dry cellulose. The sheets ofwood pulp are mercerized in the caustic soda solution in the same manneras given in Example 1. After squeezing the excess caustic soda from thewood pulp it is shredded into a fluffy mass. As in Example I, the alkalicellulose is put into a tightly closed reaction chamber in which it isstirred vigorously, while about 7 parts by Weight of gaseous ethyleneoxide are admitted to the chamber. After the ethylene oxide has reactedcompletely with the alkali cellulose the reaction mass is removed fromthe reaction chamber. This product may be dissolved in a caustic sodasolution of at least about 6% strength. It contains some undissolvedcellulosic products which may not be objectionablefor certain pu rposes,as in certain coating operations. The undissolved cellulosic materialsmay be made practically entirely soluble by the refrigerating operationto be described. Enough water is added to the reaction mass to bring thecaustic soda solution strength down to about 4.75%. The entire mass isnow refrigerated until it freezes, usually at a temperature of about 20C. The frozen mass is removed from the refrigerating chamber and allowedto melt. Enough caustic soda is added prior to melting to produce afinal 6% caustic soda solution. The solution which results is clear andviscous.

(B) The concentration of cellulose ether in the final solution producedin (A) is not high enough to make it suitable for the production offilms, filaments, and the like. To bring the ether concentration to thedesired amount for the production of films and filaments, usually about8%, the procedure is modified somewhat. After the etherification iscompleted, about one-third of the ether reaction mass is removed andneutralized by adding a 5% to 10% solution of hydrochloric or sulfuricacid. The neutralized ether is washed free of salts after which it isreturned to the two-thirds portion which was not treated with acid. Theentire mass is then diluted with water to bring the caustic sodaconcentration to 4.7 5% as in (A). By this procedure the concentrationof ether with respect to the caustic soda solution is increased to theamount necessary to give the desired final concentration. The entiremass is now refrigerated and melted as described in (A). The resultingclear viscous solution which results may be manipulated as described inExample I, section (B) to produce films, filaments and otherpyroxylin-like objects. The cellulose-ethylene oxide compound formedwhen coagulated out of the caustic soda solution is not as readilysoluble in caustic soda solutions as that formed in Example I.

E ample HI.Maln'ng compounds containz'n 12% of ethylene oxide suitablefon films of highest transparency The procedures as given in Example IIare followed except that 12 parts by weight of ethylene oxide are usedand a high grade pulp is used such as is suitable for the viscose typeof artificial silk known as rayon. After refrigeration the product maybe dissolved in a weaker solution of caustic soda compared to the 6%caustic soda solution needed to dissolve the compound containing 7% ofethylene oxide given in Example II. A 4% to 5% caustic soda solution issufiicient.

E nample [V.Mahlng water soluble compounds from wood pulp and ethyleneoxide The alkali cellulose is made as described in Example II. After theexcess caustic soda solution. is removed from the wood pulp it isallowed to stand in limited contact with the air for a period of about24: hours or more. This may be accomplished by putting the alkalicellulose in a container which does not have a tight fitting cover,thereby also preventing excessive carbonation of the alkali. The alkalicellulose is then etherified with a large amount of ethylene oxide. 75%to 95% or more ethylene oxide, depending on various factors, is used,this amount being based on the amount of cellulose used in the form ofpulp. The resulting compound may now be dissolved in water. The alkalimay be neutralized Witha mineral. acid, such as hydrochloric orsulphuric. Coagulation does not take place. The salts of hydrochloricand sulphuric acid which are formed when the caustic soda is neutralizedby these acids may be removed from the compound by dialysis. If aceticacid has been used to neutralize the caustic soda then the resultingsodium acct-ate may be removed by treating the entire mass with alcohol.Since the sodium acetate is soluble in alcohol this effects a separationfrom the cellulose compound.

E wample V.Etherifieaton with ethylene owide dissolved in solvents Thealkali cellulose is prepared as described in either Examples I or II. A20% solution of ethylene oxide in benzol is made. The wet alkalicellulose is submerged in the benzol solution of ethylene oxide for 48hours at a temperature of about 4 C. aft-er which the excess of benzoland oxide is removed as by centrifugiing or distillation. The resultingcompound of cellulose and ethylene oxide is soluble in weak caustic sodasolutions and is treated as described in Example I to form otherproducts therefrom. The etherification of alkali cellulose apparentlytakes place much more slowly in the liquid phase than in the vaporphase.

E mample Vl.Ethem'fieatz'on with liquid ethylene oxide The alkalicellulose is made as described in Example I. The wet alkali celluloseafter squeezing out the excess of caustic soda is submerged in liquidethylene oxide. After being submerged or wetted with the liquid for aperiod of 20 hours at 4 C. it is removed and the excess ethylene oxidedriven off by warming. The resulting product is soluble in dilutecaustic soda solutions and may be coagulated as described in Example Iand used for various purposes. If it is desirable to increase thetemperature so as to cut down the time of etherification pressurevessels must be used.

Example Vll.Mahing compounds contain ing 12.4% of propylene oxide Thealkali cellulose is made as is described in Example I. About 100 partsby weight of fluffy fibrous alkali cellulose is introduced into thereaction chamber. Thereaction chamber is evacuated after which therequisite amount of propylene oxide vapor is introduced into it. About12.4 parts by weight of propylene oxide are used. Since the propyleneoxide boils at 35 C. it is desirable to keep the reaction chamber atthat temperature or slightly higher if evacuation is not used. After thepropylene oxide has been completely absorbed by the alkali cellulose theresulting product resembles that after etherification described inExample II. The procedure for isolating this compound and using it inthe various forms follows the procedure outlined in Example II.Compounds containing varying amounts of propylene oxide may be madeaccording to the procedures outlined in Examples I, III, IV, V and VI,having due regard to the differences in the two compounds.

About 100 parts by weight of ordinary corn starch, containing 10% ofmoisture, is mixed with about 200 parts by weight of 20% caustic sodasolution. The mixing must be thorough until the reaction is completed.The alkali starch is then introduced into the treating cylinder withmore agitation and treated with the ethylene oxide. The ethylene oxideis absorbed by the alkali starch. About 15 to 17 parts by weight ofethylene oxide gives a water soluble, translucent co1npound that isdoughy but sticky in consistency. The excess caustic soda may bedialyzcd from the water soluble starch compound. Acetic acid may be usedto neutralize the excess caustic soda and the resulting sodium acetateseparated from the carbohydrate compound by ethyl alcohol.

Example IX.Ma/eing cellulose hyclrcwyethyl ether using ethylenechlorhyelm'u Method A.-The wet alkali cellulose, made as described inExample I, is introduced into a tightly closed reaction chamber having astirrer and a false perforated bottom. Into the chamber underneath thefalse bottom, equal parts of a 20% caustic soda solution and ethylenechlorhydrin of specific gravity 1.15 are introduced. Enough of the twosolutions are used to generate about 20 parts by weight of ethyleneoxide. The bottom of the reaction tank is then warmed so as to generatethe ethylene oxide more quickly. After the ethylene oxide is completelyevolved and has reacted with the alkali cellulose the resulting compoundof cellulose and ethylene oxide is removed from the reaction chamber.This compound is similar to that obtained in Example I and the balanceof the procedure is the same as that given in Example I.

Method B.In this method the ethylene oxide is generated by the causticsoda used to mercerize the cellulose, enough caustic soda solutionremaining in the alkali cellulose so that it will react with theethylene chlorhydrin to form ethylene oxide. Two pounds of wood pulp arewet with 12 parts by weight of 20% caustic soda solution at about 22 C.for a few minutes and only the excess is drained of}? to leave a soakedalkali cellulose weighing 7 to 9 times the air dry weight of thecellulose. The alkali cellulose is then introduced into a containerwhich may be made tight and refrigerated at about 0 C. for about 30minutes. Six parts by weight of ethylene chlorhydrin of 1.2 specificgravity are added to the alkali cellulose containing the excess causticsoda solution. The reaction mass is stirred continuously at about 6 C.for one or two hours and then allowed to come to room temperature andstirred at this temperature for 24 to 48 hours. Heating to about 30 C.hastens the reaction. The resulting compound is soluble in dilutecaustic soda solution.

Method C.The soda cellulose is made as in Example I except that a 4.0%caustic soda solution is used. After squeezing out the excess causticsoda solution the mixture is shredded into a wet fluffy fibrous mass.100 parts by weight of cellulose are converted into wet fluffy sodacellulose and treated with about 18 parts by weight of anhydrous ornearly anhydrous ethylene chlorhydrin. This amount of chlorhydrin isequivalent to about 9 parts by weight of ethylene oxide. The mixture isstirred vigorously and preferably in a closed container. The temperaturemay be at room temperature or lower. The reaction is complete within anhour or two. The resulting reaction product may then be diluted withwater to bring the caustic soda concentration to about 4.75% NaOI I. Itmay then be frozen as described in Example II. Instead of bringing thecaustic soda concentration of the reaction mass to 4.75% it may first bediluted with water to bring the caustic soda concentration to about 6%to 10% after which it is neutralized with an acid. This precipitates theother, which is washed with water after which it is again wet with 4.75NaOH and preferably to a concentration of 8.5% ether so that it may beused for the manufacture of films and filaments. The refrigeratingoperation then proceeds as in Example II.

E acample X.Mahiuy cellulose (l lhyelrmey propyl ether The alkalicellulose is made as described in Method C of Example IX. To 100 partsby weight of the cellulose in the form of wet, shredded fluffy alkalicellulose about 22.5 parts by weight of anhydrous or nearly anhydrousglycerol monochlorhydrin are added and the etherification carried out asdescribed with the ethylene chlorhydrinin Method C of Example IX. Thisamount of the glycerol monochlorhydrin is equivalent to about 9%ethylene oxide. The balance of the procedure is like that given for theethylene chlorhydrin in Method C of Example TX. The resulting ether isVery similar in its properties to the ether of an equivalent ethyleneoxide content whether made from the gaseous ethylene oxide or theethylene chlorhydrin.

Example X[.Hy Zr0my-ethyl-cellulose ether benzoate 100 parts by weightof alpha cellulose chemical wood pulp containing 8.5% moisture issteeped in a 30% caustic soda solution at 18 C. for minutes. The sodacellulose is squeezed to about 350 parts by weight, shredded, and aged21 hours at 19 C. The alkali cellulose is churned in a closed container2% hours with 12 parts by weight of ethylene oxide. The ether is furtheragitated with 15 parts by weight of benzoylchloride for 30 minutes atroom temperature in the presence of an excess of benzol. The resultingalkali-ether-benzoate is centrifuged to remove the benzol, dissolved in4.75% caustic soda, frozen and thawed as in Examples II or III. A 7.5%solution of the resulting compound is made up in 7.5% solution ofcaustic soda for use in making films, filaments and other products. Theprocess may be reversed, that is, the alkali cellulose may be firstbenzoylated and then etherified with the ethylene oxide with noappreciable differences in the final product.

The claims of the present application differ from those of the companionapplications on this same disclosure in referring particularly to theprocess of etherifying using halohydrins, such as ethylene chlorhydrin,to form the new ethers herein described.

This application is a continuation in part of applicants earlierapplication, Serial Number 345,214, filed March 7, 1929, and which hassince become abandoned. Certain subject matter not claimed in thepresent application is claimed in my copending applications Serial Nos.475,250 and 475,251, filed August 14, 1930, and in Serial Nos. 477,752and 477 ,753, filed August 25, 1930, as divisions of this applicationSerial No. 475,249, filed August 14, 1930, one of which divisionalapplications, No. 477,752, issued June 14, 1932 as Patent No. 1,863,208.

I claim:

1. The method of making an hydroxyalphyl ether of a carbohydratewhiclrcomprises treating the carbohydrate with a caustic alkali solutionof substantially less than strength and not less than substantially 40%strength to form an alkali carbohydrate, removing excess of causticalkali solution to leave a moistened alkali carbohydrate and mixing themoist alkali carbohydrate with a substantially anhydrous alphylhalohydrin in substantially the proportions theoretically necessary forthe desired ether, whereby to react the mass to form the ether in theabsence of a substantial amount of water.

2. The method of making an hydroxyethyl ether of a carbohydrate whichcomprises treating the carbohydrate with a caustic alkali solution ofsubstantially less than 50% strength and not less than substantially 40%strength to form an alkali carbohydrate, removing excess of causticalkali solution to leave a moistened alkali carbohydrate and mixing themoist alkali carbohydrate with substantially anhydrous ethylenechlorhydrin in substantially the proportions theoretically necessary forthe desired ether, whereby to react the mass and form the ether in theabsence of a substantial amount of water.

3. The method of making an hydroxyalphyl ether of cellulose whichcomprises treating cellulose with a caustic alkali solution ofsubstantially less than 50% strength and not less than substantially 40%strength to form an alkali cellulose, removing some excess of causticalkali solution to leave a moistened alkali cellulose, and mixing themoist alkali cellulose with a substantially anhydrous alphyl halohydrinin substantially the proportions theoretically necessary for the desiredether, whereby to react the mass and form the ether in the absence of asubstantial amount of water.

4. The method of making an hydroxyethyl ether of cellulose whichcomprises treating cellulose with a caustic alkali solution ofsubstantially less than 50% strength and not less than substantially 40%strength to form an alkali cellulose, removing some excess of causticalkali solution to leave a moistened alkali cellulose, and mixing themoist alkali cellulose with a substantially anhydrous ethylenechlorhydrin in substantially the proportions theoretically necessary forthe desired ether, whereby to react the mass to form the ether in theabsence of a substantial amount of water.

5. The method of making an hydroxyethyl ether of cellulose whichcomprises treating cellulose with a substantially 40% caustic sodasolution to form an alkali cellulose, removing the excess of causticsoda solution to form a moist alkali cellulose and reacting the moistalkali cellulose with substantially anhydrous ethylene chlorhydrin inthe proportion of twenty-seven parts by weight of chlorhydrin to 100parts by weight of original cellulose, whereby to form the ether in theabsence of a substantial amount of water.

6. The method of making a dihydroxy propyl ether of a carbohydrate whichcomprises treating the carbohydrate with a caustic alkali solution ofsubstantially less than 50% strength and not less than substantially 40%strength to form an alkali carbohydrate, removing excess of causticalkali solution to leave a moistened alkali carbohydrate, and mixing themoist alkali carbohydrate with substantially anhydrous glycerolmonoclilorhydrin in substantially the proportions theoreticallynecessary for the desired ether, whereby to react the mass and form theether in the absence of a substantial amount of water.

7. The method of making a dihydroxy propyl ether of a carbohydrate whichcomprises treating the carbohydrate with a caustic alkali solution oi:substantially less than 50% strength and not less than substantially 40%strength to "form an alkali carbohydrate, removing excess oi causticalkali solution to leave a moistened alkali carbohydrate, and mixing themoist alkali carbohydrate with substantially anhydrous glycerolmonochlorhydrin in substantially the proportions theoretically necessaryfor the desired ether, whereby to react the mass and form the ether inthe absence of a substantial amount of water.

8. The method of making a dihydroxy propyl ether of cellulose whichcomprises treating cellulose with a caustic alkali solution ofsubstantially less than 50% strength and not less than substantially 40%strength to form alkali cellulose, removing some excess of causticalkali solution to leave a moistened alkali cellulose, and mixing themoist alkali cellulose with substantially anhydrous glycerolmonochlorhydrin in substantially the proportions theoretically necessaryfor the desired ether, whereby to react the mass and form the ether inthe absence of a substantial amount of water.

9. The method of making a dihydroxy propyl ether of cellulose whichcomprises treating cellulose with a caustic alkali solution Ofsubstantially less than 50% strength and not less than substantially 40%strength to form alkali cellulose, removing excess of caustic solutionto leave a moistened alkali cellulose, and mixing the moist alkali cellulose with substantially anhydrous glycerol monochlorhydrin insubstantially the proportions theoretically necessary for the desiredether, whereby to react the mass and form the ether in the absence of asubstantial amount of water.

10. The method of making a dihydroxy propyl ether of eelluluose whichcomprises treating cellulose with a substantially 40% caustic sodasolution to form an alkali cellulose, removing the excess of causticsoda solution to form a moist alkali cellulose, and reacting the moistalkali cellulose with substantially anhydrous glycerol monoehlorhydrinin the proportion 01 22.5 parts by weight of the chlorhydrin to 100parts by Weight of original cellulose, whereby to form the ether in theabsence of a substantial amount of water.

11. The method of making dihydroXy propyl ether of cellulose whichcomprises reacting an alkali cellulose prepared with a caustic alkali ofsubstantially less than 50% strength and not less than substantially 40%strength with glycerol monochlorhydrin in the absence of a substantialamount of Water, whereby to form the ether.

In testimony whereof, I have subscribed my name.

ARLIE W. SCHORGER.

